71 lines
1.9 KiB
C++
71 lines
1.9 KiB
C++
#include "PromAddressDriver.h"
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#define ADDR_CLK_HI A3
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#define ADDR_CLK_LO A4
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#define ADDR_DATA A5
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void PromAddressDriver::begin()
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{
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// The address control pins are always outputs.
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pinMode(ADDR_DATA, OUTPUT);
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pinMode(ADDR_CLK_LO, OUTPUT);
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pinMode(ADDR_CLK_HI, OUTPUT);
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digitalWrite(ADDR_DATA, LOW);
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digitalWrite(ADDR_CLK_LO, LOW);
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digitalWrite(ADDR_CLK_HI, LOW);
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// To save time, the setAddress only writes the hi byte if it has changed.
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// The value used to detect the change is initialized to a non-zero value,
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// so set an initial address to avoid the the case where the first address
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// written is the 'magic' initial address.
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setAddress(0x0000);
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}
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// Set a 16 bit address in the two address shift registers.
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void PromAddressDriver::setAddress(word address)
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{
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static byte lastHi = 0xca;
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byte hi = address >> 8;
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byte lo = address & 0xff;
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if (hi != lastHi)
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{
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setAddressRegister(ADDR_CLK_HI, hi);
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lastHi = hi;
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}
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setAddressRegister(ADDR_CLK_LO, lo);
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}
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// Shift an 8-bit value into one of the address shift registers. Note that
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// the data pins are tied together, selecting the high or low address register
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// is a matter of using the correct clock pin to shift the data in.
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void PromAddressDriver::setAddressRegister(uint8_t clkPin, byte addr)
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{
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// Make sure the clock is low to start.
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digitalWrite(clkPin, LOW);
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// Shift 8 bits in, starting with the MSB.
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for (int ix = 0; (ix < 8); ix++)
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{
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// Set the data bit
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if (addr & 0x80)
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{
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digitalWrite(ADDR_DATA, HIGH);
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}
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else
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{
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digitalWrite(ADDR_DATA, LOW);
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}
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digitalWrite(clkPin, HIGH); // Clock in a bit
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digitalWrite(clkPin, LOW); // Reset the clock pin
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addr <<= 1;
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}
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}
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